There have been numerous efforts to utilize a polyurethane composition in the textile industry. Especially in the tufted carpet industry, it will be recognized that it is necessary to secure the face yarns in the primary backing by means of an adhesive, and it is of course desirable to provide a cushion or padding for the carpeting.
Latex has been used extensively for securing the face yarns in the primary backing, and for adhering a secondary backing to the primary backing. While this technique has been commercially successful, the use of latex is undesirable both because of the total weight of the resulting product, and because of the energy necessary to dry the latex after application.
In many instances, a pad is fixed directly to the carpeting so the carpet can be installed without the separate installation of a pad. Again, latex has been used extensively to provide such a pad, the latex being foamed, then dispensed onto the carpet backing, doctored to a uniform thickness, then dried or cured. The curing of the foamed latex requires a large amount of energy because of the quantity of water that must be removed from the foamed latex.
To overcome the disadvantages of the latex, there have been efforts to utilize a polyurethane for the cushioned backing for carpet and the like. The difficulties with polyurethane include the fact that the components for producing a polyurethane, when placed directly on textile goods will quickly flow through the goods. Thus, if the polyurethane components are placed on the primary carpet backing, the material will flow into the face yarns of the carpet. Because of this fact, the prior art utilization of polyurethane for textile coatings have employed several different methods to apply the polyurethane to the textile goods. British Pat. No. 1,302,213 discloses the spraying of the components onto a piece of material, and allowing the components to react to form a blown polyurethane. U.S. Pat. No. 4,278,482 discloses a similar process wherein the components are sprayed onto the textile goods. The system disclosed in U.S. Pat. No. 4,132,817 includes the dispensing of the polyurethane components onto an impervious belt, allowing the components to react to form a blown polyurethane, and applying the textile material to the polyurethane while the material is blowing.
The prior art systems wherein the polyurethane components are sprayed onto a substrate have generally been found to be unacceptable because of the difficulty of obtaining uniform mixing of components in application of the components. Since the polyurethane components react with one another to produce heat, and the heat accelerates the reaction, it will be understood that a small difference in thickness of application of the components will produce a large difference in the blown polyurethane composition. A mechanical frothing of the polyurethane components is both difficult and expensive since the components must be mechanically frothed and blown, then external heat must be applied to effect a cure. The application of the components to an impervious belt requires an elaborate mechanism, and generally the use of release agents or the like so that such a process becomes quite expensive.